We know the answers now, of course: all those aeons of mountain building and destruction, the rise and fall of the seas, the compaction, pressure, heating, cooling, sedimentation, erosion. The Earth is a rocky labyrinth.

Was, anyhow. It’s getting kind of simpler, even as I stand here.

Strange how Burnet seems to have been right all along, though, doesn’t it?

It had been a couple of years since the Moonseed made the mantle so hot that plate tectonics effectively stopped. The plates were too hot to behave in the rigid way they used to; and the rock of the mantle was just too runny to support big horizontal movements.

It had been thought that would reduce the volcanism for a time, but it didn’t turn out that way.

Still, the map of Earth was recognizable. Just.

The ocean plates were softening and melting back. The continents showed up in his images as black and dark islands in glowing oceans, the ancient granite cratons surrounded by crumpled greenstone. The cratons were the cores around which the continents had accreted in the first place, crust slabs which had formed in the centre of ancient mantle convection cells; now they were being uncovered once more.

It was as if, Henry thought, someone was winding back Earth’s evolution.

And there were giant mantle plumes breaking out all over the planet, flood lavas, volcanic domes, cones and even coronae — features never seen on Earth before, only on lost Venus, basaltic domes surrounded by annuli of ridges and grooves. Nowhere was left untouched in the catastrophic resurfacing of the planet.

Hardly anything of the works of humanity survived.

There was one consolation, though. For a time, Earth was the youngest place in the Solar System.

…I want to tell you how much I admire you people up there. My God, you guys think big. Your schemes to bring in comets to graze the Moon’s atmosphere and increase the volatile content. Rebuilding the crater walls and lunar mountains that are already getting eroded by the rain. No plate tectonics on the Moon, to maintain the carbon and oxygen cycles: so you’ll bake the silicate rocks into glass, drive out the carbon dioxide that’s weathered there, and reverse the erosion… Jesus.

I’m not sure if I agree with your projections that you can reduce the time to true terraforming to a thousand years, but I haven’t had the time to run the math. I don’t think you ought to concern yourself with the objections of the Siberians who have colonized farside. They aren’t even human; let them build their own damn world.

But you talk about using the extremal black holes from the Earth’s debris to tip the Moon, to give it seasons, then to spin it up. It’s a nice idea. A final gift from the Earth, to its daughter…